Science & Tech · Science & Environment · 2 hrs ago
Colorado River's Upper Basin Lost More Groundwater in 2020–22 Drought
The Colorado River’s upper basin lost nearly twice as much groundwater as the lower basin during the 2020–22 drought.
Researchers from Virginia Tech and Indiana University used NASA satellites to track groundwater changes across the basin from 2003 to 2023.
The river supplies about 40 million people in seven states, and irrigation uses 70% to 80% of its water.
The upper basin lost about 4.6 trillion gallons in those three years, while the lower basin lost about 2.5 trillion gallons.
Groundwater shortages followed surface-water shortages in the upper basin, while in the lower basin groundwater began falling before reservoirs did, possibly because of pumping.
The basin has lost about 15 trillion gallons since 2004, and a wet year in 2023 refilled only part of the gap; wet years have not made up for dry ones since 2005.
The Colorado River’s Upper Basin lost about 4.6 trillion gallons of groundwater during the 2020–22 drought, nearly twice the Lower Basin’s loss.
Researchers used NASA satellite data to track groundwater across the basin from October 2003 through September 2023.
Upper Basin groundwater losses averaged roughly 1.6 trillion gallons a year during the drought, about twice the Lower Basin rate.
The Upper Basin’s groundwater had been declining since 2012 and reached its lowest point in 2022.
A wet 2023 replenished some groundwater, but the researchers said wet years have not made up for dry years since 2005.
- Who
- Researchers Esther Oyedele and Susanna Werth of Virginia Tech, with a colleague at Indiana University.
- What
- The Upper Basin lost about 4.6 trillion gallons of groundwater during the drought, nearly twice the Lower Basin’s loss.
- When
- During the 2020–22 drought.
- Where
- The Upper Basin of the Colorado River Basin.
- Why
- The researchers studied groundwater loss and how it related to surface-water shortages. They attributed the contrasting pattern between basins to differences in how groundwater responds to shortages.
This story does not have two clearly opposing sides.
Researchers tracked groundwater changes across the Colorado River Basin using satellite data.
Upper Basin groundwater began sliding, according to the article.
The drought brought the Upper Basin’s groundwater loss to about 4.6 trillion gallons.
Upper Basin groundwater reached its lowest point in the record described.
A wet year refilled some of the groundwater gap.
- Upper Basin groundwater loss
- About 4.6 trillion gallons (17.5 cubic kilometers) in 2020–22
- Lower Basin groundwater loss
- About 2.5 trillion gallons (9.4 cubic kilometers) in 2020–22
- Upper Basin annual loss rate
- Roughly 1.6 trillion gallons (6 cubic kilometers) a year
- Satellite record
- October 2003–September 2023
- Basin-wide water loss
- About 15 trillion gallons (58 cubic kilometers) since 2004, with groundwater accounting for about half
What people are saying
We generally think of the Upper Basin as more resilient because of its snowmelt-driven recharge.
I did not expect to see so much groundwater loss there during the recent drought.
What surprised me even more was that groundwater did not track surface-water shortages in the same way in the Upper and Lower Basins.